NASA estimated Monday it will cost $104 billion to return astronauts to the moon by 2018 in a new rocket that combines the space shuttle with the capsule of an earlier NASA era.

NASA Administrator Michael Griffin, in unveiling the new lunar exploration plan announced by President Bush last year, said he is not seeking extra money and stressed that the space agency will live within its future budgets to achieve this goal.

He dismissed suggestions that reconstruction of the Gulf Coast in the wake of Hurricane Katrina might derail the program.

"We're talking about returning to the moon in 2018. There will be a lot more hurricanes and a lot more other natural disasters to befall the United States and the world in that time, I hope none worse than Katrina," Griffin said at a news conference.

"But the space program is a long-term investment in our future. We must deal with our short-term problems while not sacrificing our long-term investments in our future. When we have a hurricane, we don't cancel the Air Force. We don't cancel the Navy. And we're not going to cancel NASA."

The $104 billion price tag, spread over 13 years, represents 55 percent of what the Apollo moon-landing program cost measured in constant dollars, Griffin said. Apollo spanned eight years.

CBS News Correspondent Wyatt Andrews reports that the new space vehicle, designed to replace the shuttle, looks like an old-fashioned space capsule (video).

The new space vehicle design uses shuttlelike rocket parts, an Apollo-style capsule and lander capable of carrying four people to the surface. The rockets — there would be two, a small version for people and a bigger one for cargo — would come close in height to the 363-foot Saturn 5 moon rocket. They would be built from shuttle booster rockets, fuel tanks and main engines, as well as moon rocket engines. The so-called crew exploration vehicle perched on top would look very much like an Apollo capsule, albeit larger.

"Think of it as Apollo on steroids," Griffin said.

The crew exploration vehicle would replace the space shuttle, due to be retired in 2010, but not before 2012 and possibly as late as 2014 depending on the money available, Griffin said. It could carry as many as six astronauts to the international space station.

If all goes well, the first crew would set off for the moon by 2018 — or 2020 at the latest, the president's target year.

Andrews reports that just like in the heyday of the Apollo missions, 36 years ago, astronauts will land on and take off from the moon using a separate lunar lander. But this time, there will be four astronauts — not two — staying at least a week, rather than two or three days.

The Earth-returning capsule would be able to parachute down on either land or water, although land is preferable, most likely at Edwards Air Force Base in California.

Griffin said NASA did not set out to mimic Apollo with the new spacecraft and that many options were considered over the summer.

"It's a significant advancement over Apollo. Much of it looks the same, but that's because the physics of atmospheric entry haven't changed recently," he said. "...We really proved once again how much of it all the Apollo guys got right."

The space agency's ultimate goal is to continue on to Mars with the same type of craft, but Griffin said there is no current timetable for Mars expeditions.

NASA believes the crew exploration vehicle would be far safer than the space shuttle, largely because of an old-style escape tower that could jettison the capsule away from the rocket in the event of an explosion or fire.

Two shuttles and 14 astronauts have been lost over 114 flights, Challenger in 1986 and Columbia in 2003. Nonetheless, NASA puts the existing failure rate for the shuttles at 1-in-220. The failure rate for the crew exploration vehicle is put at 1-in-2,000.